In general, a specimen liquid sensor unit (specimen liquid sensor apparatus) is known, which includes a specimen liquid sensor holding a specimen liquid and capable of converting an input electric signal in accordance with characteristics or components of a specimen liquid and a reader transmitting and receiving an electric signal to and from the specimen liquid sensor.
As a specimen liquid sensor, a SAW sensor of which size can be reduced attracts attention, because the price of the SAW sensor can be reduced through mass production, and the detection circuit can be realized with a simple electric circuit (Non Patent Document 1). The SAW sensor has an input electrode for generating a surface acoustic wave (SAW) from an electric signal and an output electrode for receiving the SAW on the upper surface of the substrate. In the SAW sensor, a metal film having an antigen fixed on the surface is arranged between these electrodes, and the SAW sensor analyzes the output signal resulting from bonding of the antigen and the antibody and find the component of the specimen liquid based on the change in the phase characteristics of the SAW.